OBTAINING CRITICAL PHASE INFORMATION FOR THE DESIGN OF REFRACTORY HIGH-ENTROPY SUPERALLOYS
Abstract
Refractory high entropy alloys (RHEAs) are known to have good resistance to thermal softening and thus exceptional high temperature strength. Recently RHEAs with superalloy-like microstructure, i.e., discrete B2 particles surrounded by a continuous BCC matrix, were discovered. These alloys were named refractory high entropy superalloys (RHESAs). The superalloy microstructure further enhances the high temperature performances, giving RHESAs great potential to operate at temperatures higher than those of Ni-based superalloys. One of the key issues in the development of RHESAs is the engineering of the main strengthening phase, the ordered B2 phase. The composition, temperature stability and volume fraction of the B2 phase directly affect the performance and applicability of RHESAs over Ni-based superalloys. However, the control of the B2 phase in RHESAs is very challenging. The B2 phase cannot be formed between any two composing elements in existing RHESAs and is only found in ternary or more complex subsystems. However, available ternary phase diagrams for B2-containing refractory systems are largely incomplete, and phase diagrams for higher-order systems are essentially not available. Due to the lack of such fundamental knowledge, the design of RHESAs by either conventional metallurgical approach or computational tools such as CALPHAD is extremely difficult. Thus, the acquisition of fundamental experimental data is urgently needed. In this proposal, the equilibrium phase data around the B2 phase region in selected RHESA and their key ternary subsystems will be investigated, and partial phase diagrams at three different temperatures will be obtained. Thus, knowledge regarding the stability of the B2 phase and the BCC+B2 phase region will be revealed. These knowledge will provide guidance for the design of RHESAs and lay the foundation for future development of theoretical models and computational tools.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 11, 2021
- Source ID
- FA23862014086
Entities
People
- Ming-hung Tsai
Organizations
- Air Force Office of Scientific Research
- National Chung Hsing University
- United States Air Force